Evaluation of FMH QuikQuant for the detection and quantification of fetomaternal hemorrhage

Abstract

The Kleihauer-Betke test (KBT) is the most widely used assay for fetomaternal hemorrhage (FMH) detection in rhesus D negative women. In the current study, we sought to evaluate the performance of a flow cytometry (FCM) kit (FMH QuikQuant) using an anti-HbF antibody. Eighty-three pregnant women, 58 umbilical cord blood (UCB) dilutions in adult blood, and 6 control samples were tested in parallel with FCM and KBT. Firstly, we compared for each assay, on the 58 UCB preparations, results obtained to dilutions prepared. FCM results showed an excellent correlation (r = 0.97), a high reproducibility with a coefficient of variation lower than 20% for values reaching 10 fetal RBCs. KBT values were correlated (r = 0.94) but exhibited a poor reproducibility. Then, we compared both techniques on all samples. FCM showed a good correlation with KBT (r = 0.87) but the KBT exhibited a systematic overestimation of the FMH. For 8 out of 83 pregnant women, KBT was positive. Five were concordant with FCM results (KBT+/FCM+). On the three discordant (KBT+/FCM-), 2 were finally classified as false positive of the KBT because a second control sample was negative and additionally, FCM identified an increased rate of F cells. One discordant case (KBT+/FCM-) remained unexplained. By receiver operating characteristic analysis, we found a threshold at 4.5 RBCs for FCM with a sensitivity of 89.8% and a specificity of 93.2%. The FMH QuikQuant kit is a reliable and highly reproductive FCM method for FMH quantification.